Assoc. Prof. Stewart Schultz, PhD., from the Department of Ecology, Agronomy and Aquaculture of University of Zadar, published an interdisciplinary paper in 2011 in Limnology and Oceanography that predicted the northward migration of nudibranchs on the Pacific USA coast during climate regime shifts. It appears that the climate is shifting to a warm phase of the Pacific decadal oscillation, and just as he and his colleagues predicted, there are southern species of nudibranchs moving northward, with a beautiful example, Okenia rosacea in areas on the California coast where it has not been seen before in these numbers.

For more information, please see the links below: 

https://news.google.com/news/story?ncl=djJ2XyzNFl4i_GMtpL1u1i3Ks0x0M&q=sea+slug&lr=English&hl=en&sa=X&ei=Ly7SVJGAJcm4ogTayoKgCw&ved=0CCsQqgIwAg

http://www.news.ucsb.edu/2015/014920/roses-bloom-california-tide-pools

http://news.ucsc.edu/2015/01/sea-slugs.html

http://www.calacademy.org/press/releases/local-scientists-investigate-link-between-skyrocketing-sea-slug-populations-and